Baking oven interior coating and process therefor

ABSTRACT

A mixture of two stabilizers, one including benzene rings bearing hydroxyl substituents and the other containing divalent sulfur atoms, is effective in stabilizing tacky polymers that remain solid up to a temperature of at least 160° C. particularly polymers of isobutylene, so that the polymers give long service in the ambient atmosphere as protective layers coated on aluminum substrates and used to line the interiors of paint baking ovens. When accumulated foreign materials accumulate on the coatings, the coating and the accumulated foreign materials can be decomposed to largely volatile products by heating to a temperature substantially higher than the service temperature but not high enough to melt the metal substrate for the coating.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved material for the interior surfaceof baking ovens used at moderately high temperatures and to a liquidcomposition and a process for using this liquid composition to producethe improved interior surface material.

2. Discussion of Related Art

Baking ovens are necessary for practical utilization of many currentlycommercial high quality protective coatings, which are applied in liquidform and ultimately baked for at least several minutes and often muchlonger in order to reach their finally desired degree of chemicalreaction, so that the protective value of the coatings is maximized.Most such coatings produce gaseous emissions during the baking process,and such emitted materials can react with themselves and/or the walls ofthe baking oven to form a coating on these walls. In many cases thecoatings thus formed eventually accumulate to a sufficient thickness toconsume an undue amount of the expensively heated space within the oven,and/or the oven wall coatings themselves emit products on furtherheating that can damage the cleanliness and other quality features ofthe protective coatings on other objects that are being cured in thebaking ovens.

Accordingly, it would be advantageous to provide oven interior surfaceswith a protective covering that reduces the accumulation of unwantedadditional solid coatings thereon and/or can readily and cheaply beremoved when the accumulations on it become troublesome in any respect.However, fully suitable materials for such a protective covering foroven interior walls have previously been unavailable, particularly whenthe ovens to be protected are used for extended periods at temperaturesas high as 160° C.

DESCRIPTION OF THE INVENTION Objects of the Invention

A major object of the invention is to provide an improved oven interiorsurfacing material that will provide satisfactory service under usageconditions as described above. Another concurrent or alternative objectis to provide a liquid composition that can conveniently be coated ontoa metal backing and then converted by a practical process into animproved oven interior surfacing material. Still another concurrent oralternative objective is to provide an interior surfacing material withtack, so that particulate matter will have a greater tendency to adhereto it rather than remaining in suspension in the gaseous atmospherewithin the oven, where it would be more likely to blemish the surface ofsome object being baked in the oven. Other objects will be apparent fromthe description below.

General Principles of Description

Except in the claims and the specific examples, or where otherwiseexpressly indicated, all numerical quantities in this descriptionindicating amounts of material or conditions of reaction and/or use areto be understood as modified by the word “about” in describing thebroadest scope of the invention. Practice within the numerical limitsstated is generally preferred, however. Also, unless expressly stated tothe contrary: percent, “parts of”, and ratio values are by weight; theterm “polymer” includes “oligomer”, “co-polymer”, “terpolymer”, and thelike; the first definition or description of the meaning of a word,phrase, acronym, abbreviation or the like applies to all subsequent usesof the same word, phrase, acronym, abbreviation or the like and applies,mutatis mutandis, to normal grammatical variations thereof, thedescription of a group or class of materials as suitable or preferredfor a given purpose in connection with the invention implies thatmixtures of any two or more of the members of the group or class areequally suitable or preferred; specification of materials in ionic formimplies the presence of sufficient counterions to produce electricalneutrality for the composition as a whole; and any counterions thusimplicitly specified preferably are selected from among otherconstituents explicitly specified in ionic form, to the extent possible;otherwise such counterions may be freely selected, except for avoidingcounterions that act adversely to the objects of the invention.

SUMMARY OF THE INVENTION

It has been discovered that metal substrates having surfaces thatcontain at least 45% of aluminum can be coated with a combination oftacky solid and two types of anti-oxidants in solvent and then convertedto a solid coating by expelling most of the solvent by heating, toproduce an excellent surfacing material for the interior of bakingovens. The outer “coated” side of this surfacing material, which facesthe interior space within the oven when in use, remains tacky for atleast a few days, even when aged at temperatures in excess of 160° C.When excessive undesirable deposits accumulate on this coated side ofthe surfacing material, the coating layer can easily be removed byheating to a higher temperature such as 275° C. in the presence ofoxygen, such as in the ambient natural atmosphere. The covering thendecomposes cleanly, along with most organic residues accumulated on it,and any non-combustible constituent(s) of the accumulated residues caneasily be removed from the oven. The interior walls of the oven can thenbe recoated with a liquid composition according to the invention andheated at an appropriate temperature to convert the liquid coating thusformed to a solid protective coating, so that the oven is ready forcontinued use.

One embodiment of the invention is accordingly a suitable liquid coatingcomposition which comprises, preferably consists essentially of, or morepreferably consists of:

(A) a component of polymeric material that (i) is solid and (ii) hastack sufficient to be sensed by a brief touch by a normal human finger,both throughout a temperature range from 25 to 160° C.;

(B) a first stabilizing component selected from the group consisting ofmolecules and moieties¹ thereof, exclusive of molecules and moietiesthereof that constitute component

¹Ordinarily, each of components (B) and (C) preferably is selected fromindividual and distinct molecules containing the chemical featuresrecited for each component. However, all of the chemical featuresrequired for both the first and second stabilizing components could beincorporated into a single molecule and/or could be grafted onto polymermolecules that are part of component (A). The phrase “moieties thereof”in the description of components (B) and (C) is intended to embracethese possibilities. However, if an entire molecule present in acomposition according to the invention includes all the chemicalfeatures required for component (B) or (C) and does not include all thechemical features required to constitute part of any other of components(A) through (C), the entire molecule rather than any moiety thereof isto be considered as part of the component (B) or (C) of which it canconstitute a part. On the other hand, if a molecule present in acomposition according to the invention includes both all the chemicalfeatures required to constitute a part of component (B) or (C) and alsoall the chemical features required to constitute a part of at least oneother of components (A) through (C), only any smallest continuouslybonded moiety of such a molecule that contains all the necessaryfeatures recited for component (B) is to be considered part of component(B) and only any smallest continuously bonded moiety of such a moleculeponet (A), each of the first stabilizing component molecules or moietiesthereof containing (i) at least one benzene ring that is substitutedwith at least one hydroxyl moiety and at least two alkyl moieties and(ii) at least one carbon atom bonded by single bonds to four othercarbon atoms, alternatively called a “tertiary” carbon atom;

(C) a second stabilizing component selected from the group consisting ofmolecules or moieties thereof, exclusive of molecules or moietiesthereof that constitute component (A) or (B), each of said molecules ormoieties thereof containing (i) at least one divalent sulfur atom thatis bonded to two distinct carbon atoms and (ii) at least two carboxyl orcarboxylate moieties; and

(D) a component of solvent, exclusive of materials that constitute partof any of the preceding components, the solvent having a freezing pointbelow 20° C. and a boiling range at a pressure of 1 bar that begins at atemperature that is at least about 70° C. and ends at a temperature thatis not more than 230° C. and being present in sufficient amount todissolve together into a single solution all of components (A), (B), and(C) to form a solution that is liquid at 25° C.; and, optionally,

(E) a continuous liquid phase, preferably water, into which the solutionformed by components (A) through (D) above is emulsified but remains asa separate phase,

that also includes all the preferred features of a preferred embodimentof component (B) is to be considered part of a particular preferredembodiment of component (B), and if the remainder of that moleculecontains all the chemical features necessary to constitute a part ofcomponent (C), that remainder constitutes part of component (C), unlessthe remainder also includes all the chemical features required toconstitute component (A), in which instances only any smallestcontinuously bonded moiety of such remainder that contains all thenecessary and/or preferred features recited for component (C) is to beconsidered part of component (C), and the residue is to be consideredpart of component (A). If a molecule present in a composition accordingto the invention does not contain all the chemical features required forcomponent (B) but does contain all the chemical features required toconstitute both components (A) and (C), only any smallest continuouslybonded moiety of such a molecule that contains all the necessaryfeatures recited for component (C) is to be considered part of component(C) and only any smallest continuously bonded moiety of such a moleculethat also includes all the preferred features of a preferred embodimentof component (C) is to be considered part of a particular preferredembodiment of component (C), and the remainder of the molecule is to beconsidered part of component (A). said liquid coating composition havingthe property that, when a volume of the composition is formed into alayer not more than 0.5 millimeter in thickness and heated to at leastone temperature not greater than 160° C., in a space containing gashaving a pressure no higher than that of the ambient natural atmosphere,at least components (A), (B), and (C) of the composition will beconverted within a time of 60 minutes into a coherent tacky solid and atleast a preponderant part of components (D) and (E) will be volatilized.

Another embodiment of the invention is a process comprising, preferablyconsisting essentially of, or more preferably consisting of, the stepsof:

(I) providing (i) a metallic substrate having at least one surfaceconstituted of not less than 45% of aluminum and (ii) a liquidcomposition according to the invention as described above;

(II) forming at least part of the liquid composition provided in step(I) into a liquid coating over at least part of the surface constitutedof not less than 45% of aluminum on the substrate also provided in step(I); and

(III) heating the liquid coating formed in step (II), while said coatingis in place over the substrate surface as formed in step (II), for asufficient time at a sufficient temperature to convert it to a solid,adherent, and tacky coating over those portions of the substrate surfacethat were provided with a liquid coating in step (II).

Other embodiments of the invention include coated metal substratesprepared by a process according to the invention as described above, theuse of such coated metal substrates to line pre-existing oven interiors,a process of installing such linings in either new or pre-existingovens, ovens with interior surfaces of coated metal substrates preparedby a process according to the invention, and the like.

DETAILED DESCRIPTION OF THE INVENTION, INCLUDING PREFERRED EMBODIMENTS

Component (A) is preferably selected from hydrocarbon polymers, and morepreferably is selected from aliphatic hydrocarbon polymers in which thenumber of residual carbon-carbon double bonds in the polymer moleculesis no greater than, with increasing preference in the order given, 0.3,01.0, 0.050, 0.030, 0.020, 0.010, 0.0080, 0.0060, 0.0040, or 0.0030times the number of carbon atoms in the molecules. Most preferably, thepolymers for component (A) are homopolymers of isobutylene or copolymersof isobutylene and 1,3-butadiene. Independently of the otherpreferences, the Flory, alternatively called the Viscosity Average,molecular weight of the polymers from which component (A) is selected isat least, with increasing preference in the order given, 1.0×10⁴,2.0×10⁴, 3.0×10⁴, 3.5×10⁴, 4.0×10⁴, 4.5×10⁴, or 5.0×10⁴ andindependently preferably is not greater than 1.1×10⁶.

In general, the concentration of component (A) in a coating compositionaccording to the invention appears to make little difference in thetechnical quality of the results achieved. However, for reasons ofeconomy, it is preferable to make the concentration of component (A) ashigh as practical, with the upper limit usually being set by solubilityof the polymer in the available solvent and/or the unworkably highviscosity of a more concentrated solution. Typical practically preferredvalues are shown in the working examples below. If arrangements are madeto recover and reuse the solvent expelled from the liquid coatings afterthey are in place on the substrate to be coated in a process accordingto the invention, economic preferences may shift to more diluteconcentrations of component (A), which have lower viscosities andtherefore allow more choices of method of application to the substrate.

First stabilizing component (B) is preferably selected from molecules inwhich all benzene rings present are substituted with at least two,preferably exactly two, alkyl moieties and at least one, more preferablyexactly one, hydroxyl moiety. Independently, any benzene ring present ina molecule or moiety thereof that constitutes component (B) and that hasa hydroxyl moiety substituent preferably also has an alkyl moietysubstituent on each of both of the two carbon atoms in the benzene ringthat are nearest to the carbon atom of the benzene ring that has thehydroxyl moiety substituent. Independently of the other preferences,each of the alkyl substituents on the hydroxy-substituted benzene ringspresent in a molecule or moiety thereof that constitutes part ofcomponent (B) preferably has at least, with increasing preference in theorder given, 2, 3, or 4 carbon atoms and independently preferably has,with increasing preference in the order given, not more than 8, 6, 5, or4 carbon atoms.

Also, independently of the other preferences and of one another, in amolecule or moiety thereof that constitutes part of component (B): (i)Each alkyl moiety substituent on a benzene ring carbon atom adjacent toa hydroxyl substituted carbon atom of said—benzene ring preferably isbonded to said benzene ring via a carbon atom that is bonded by singlebonds to at least two, or more preferably at least three, other carbonatoms within the alkyl moiety and (ii) the molecule or moiety thereofthat constitutes part of component (B) also contains at least onecarboxylate ester moiety through which at least one benzene ring of themolecule or moiety thereof that has a hydroxyl substituent and at leasttwo alkyl substituents is bonded to a tertiary carbon atom in the samemolecule or moiety thereof, and more preferably has one such carboxylateester moiety for each benzene ring of the molecule or moiety thereofthat has a hydroxyl substituent and at least two alkyl substituents. Thesingle most preferred compound for component (B) is tetrakis {methylene3-(3′,5′-ditertiarybutyl-4-hydroxybenzene propionate} methane, which isthe tetra-ester of pentaerythritol with3-(3′,5′-ditertiarybutyl-4-hydroxyl phenyl) propionic acid.

Independently of the other preferences and of one another, in eachmolecule or moiety thereof that constitutes part of component (C): (i)The divalent sulfur atom preferably is bonded to at least one alkylenemoiety, more preferably to two alkylene moieties, that is or are alsobonded via their other open valence to a carboxyl or carboxylate moiety,and said alkylene moiety or moieties have at least, with increasingpreference in the order given, 1, 2, or 3 carbon atoms and independentlyhave not more than, with increasing preference in the order given, 10,8, 6, 5, 4, or 3 carbon atoms, said alkylene moieties independentlypreferably being straight chain alkylene moieties; (ii) at least one,and preferably all, of the carboxyl or carboxylate moieties present areester carboxylate moieties; and (iii) any ester carboxylate moietiespresent in the molecule or moiety thereof are esters of alcohols,preferably straight chain alcohols, that have at least, with increasingpreference in the order given, 6, 8, 10, or 12 carbon atoms per alcoholmolecule and independently preferably have not more than, withincreasing preference in the order given, 24, 22, 20, or 18 carbon atomsper alcohol molecule. The single most preferred compound for component(C) is lauryl stearyl thiodipropionate.

The concentrations of components (B) and (C) in a coating compositionaccording to the invention are preferably determined by reference to theconcentration of component (A) and/or each other, rather than by anyabsolute value, because of the variable amount of solvent that can beused as already described above. More particularly, in any particularliquid coating composition according to the invention or in a liquid orsolid coating formed therefrom by a process according to the invention:(i) The ratio of component (C) to component (B) preferably is at least,with increasing preference in the order given, 0.0:1.0, 0.30:1.0,0.40:1.0, 0.50:1.0, 0.60:1.0, 0.70:1.0, 0.80:1.0, 0.90:1.0, or 0.95:1.0and independently preferably is not more than, with increasingpreference in the order given, 2.0:1.0, 1.5:1.0, 1.40:1.0, 1.30:1.0,1.20:1.0, 1.15:1.0, 1.10:1.0, 1.05:1.0, or 1.00:1.0; and, independently,the ratio of component (B) to component (A) preferably is at least, withincreasing preference in the order given, 0.0010:1.0, 0.0020:1.0,0.0040:1.0, 0.0060:1.0, 0.0070:1.0, 0.0080:1.0, 0.0085:1.0, 0.0090:1.0,0.0093:1.0, 0.0096:1.0, or 0.0098:1.0 and independently preferably isnot more than, with increasing preference in the order given, 0.08:1.0,0.050:1.0, 0.040:1.0, 0.030:1.0, 0.025:1.0, 0.020:1.0, 0.017:1.0,0.014:1.0, 0.013:1.0, or 0.012:1.0.

In general, solvent component (D) may be chosen primarily for itssolvent properties, environmental impact, and cost, because it isexpected to have little chemical effect on the solid coating formed,from which at least most of it has been expelled. A paraffinic solventis normally preferred, and mineral spirits distilled from petroleum isparticularly preferred because of its relatively low cost and absence ofknown adverse environmental impact. Independently of the chemical natureof the solvent, its boiling range at a pressure of 1 bar preferablybegins at at least, with increasing preference in the order given, 100,110, 120, 130, 140, 145, 150, 155, or 158° C. and independentlypreferably ends at not more than, with increasing preference in theorder given, 220, 200, 190, 185, 182, 180, or 178° C.

The substrate surfaces coated in a process according to the inventionpreferably contain at least, with increasing preference in the ordergiven, 60, 75, 80, 85, 90, or 95% of aluminum. The substrate surface maybe and often is a coating over some other material, as in the aluminizedsteel that is very commonly used in constructing paint baking ovens.However, as shown in the examples and comparison examples below, directcoating over steel or most other metals produces a significantly lesslong-lived product.

Any method of application, including but not limited to brushing,curtain coating, roll coating, and spraying may be used, with thepreference factors for method of application being predominantlyeconomic—no technical performance distinction due to method ofapplication has been noted. The thickness of solid coating produced by aprocess according to the invention preferably is at least, withincreasing preference in the order given, 30, 70, 110, 150, 190, 220,250, 280, 300, 320, 340, or 350 micrometres (hereinafter usuallyabbreviated as “μm”) and, primarily for reasons of economy,independently preferably is not more than 1000, 800, 700, 600, 500, 450,or 400 μm.

The temperature at which the liquid coating formed in a processaccording to the invention is converted to a solid coating is generallynot critical, but preferably should not be so high as to diminishsubstantially the service life of the coating to be formed. Therefore,when component (A) is a butylene polymer or copolymer as preferred andthe conversion from liquid to solid coating takes place in the normalambient atmosphere, the temperature during this conversion preferably isnot greater than, with increasing preference in the order given, 200,190, 180, or 170° C. and independently, to the extent possible,preferably is, in order to complete the process in a practical time, notmore than, with increasing preference in the order given, 50, 40, 30,20, 15, 10, 5, or 1° C. less than the highest point in the boiling rangeof the solvent component in the liquid coating formed.

The invention and its benefits may be further appreciated fromconsideration of the following working examples and comparison examples.

Substrates

The following metal substrates were used and are identified in thetables below by the numbers shown below:

1. Laboratory aluminum foil weighing cups.

2. Cold rolled steel panels.

3. Aluminized steel panels.

4. Solid aluminum alloy panels.

5. Copper panels.

6. Titanium panels.

7. Galvanized steel panels.

8. Hastelloy™ C panels (predominantly nickel).

9. Stainless steel panels

10. Low coefficient of expansion silicate glass.

11. Phosphate conversion coated steel panels.

Tacky Solids

The following tacky solids {component (A) as described above} were usedand are identified in the tables by the numbers shown below.

1. VISTANEX® LM-MH low molecular weight polyisobutylene, commerciallysupplied by Exxon Chemical Co., with the following properties reportedby its supplier: penetration distance 15.4 to 11.5 millimeters(hereinafter usually abbreviated as “mm”) according to AMS Test Method210.10; minimum 97.0% non-volatile at 149° C. after 4 hours in a vacuumoven; density of 914 kilograms per cubic meter at 23° C.; Brookfieldviscosity of 50,000 to 70,000 centipoises (hereinafter usuallyabbreviated as “cps”) at 177° C.; and Flory molecular weight accordingto AMS Test Procedure 77-005 of 50,400 to 55,800.

2. VISTANEX® LM-H, which was supplied by the same source as theimmediately previous listing and is reported by its supplier to have thesame characteristics as VISTANEX® LM-MH except that (i) its penetrationdistance is 11.4 to 9.5 mm, (ii) its Brookfield viscosity is 80,900 to68,500 cps, and (iii) its Flory molecular weight is 57,600 to 67,800.

3. VISTANEX® MM L-80, which was supplied by the same source as theimmediately preceding listed item and is reported by its supplier tohave the same characteristics as VISTANEX® LM-MH except that (i) it hasa Flory molecular weight of 0.75 million to 1.05 million, and (ii) noviscosity or penetration values for the pure solids are given by thesupplier.

4. EXXON® Butyl Rubber Grade 065 was commercially supplied by ExxonChemical Co. and was reported by its supplier to be a copolymer ofpredominantly isobutylene with from 1 to 3 mole percent of 1,3-butadieneand to have a Mooney viscosity of 45±4 on the ML 1+8 (100° C.) scalewhen tested according to ASTM Test Method D 1646, modified, or ISO TestMethod 289.

Stabilizers

The following stabilizers {component (B) or (C) as described above} wereused and are identified in the tables by the numbers shown below.

1. IRGANOX® 1010 antioxidant, commercially supplied by Ciba-Geigy Corpand reported by its supplier to be tetrakis {methylene3-(3′,5′-ditertiarybutyl-4-hydroxyphenyl propionate} methane.

2. ETHANOX® 398 antioxidant, commercially supplied by Ethyl Corporationand reported by its supplier to be2,2′-ethylidene-bis-(4,6-ditertiarybutylphenyl fluorophosphite.

3. ETHANOX® 330 antioxidant, commercially supplied by Ethyl Corporationand reported by its supplier to be1,3,5-trimethyl-2,4,6-tris-(3,5-ditertiarybutyl-4-hydroxy) benzene.

4. CYANOX™ 1212 antioxidant, commercially supplied by American CyanamidCorp. and reported by its supplier to be lauryl stearylthiodipropionate.

5. CYANOX™ LTDP antioxidant, commercially supplied by American CyanamidCorp. and reported by its supplier to be dilaurylthiodipropionate.

6. 2,6-ditertiarybutyl4-methyl phenol, commonly known in the art as“BHT”.

Solvents

The following solvents {component (D) as described above} were used andare identified in the tables by the numbers shown below.

1. Mineral spirits, commercially supplied as SHELL-SOL™ 340 HT by ShellChemical Co. and reported by its supplier to have the followingcharacteristics: a specific gravity at 16° C. of 0.773; 100% totalsaturated hydrocarbons; <0.1% total aromatics; and distillation withinitial boiling point of 159° C., 10% distilled at 161° C., 50%distilled at 163° C., 90% distilled at 169° C., and completely distilledat 177° C.

2. D-Limonene

Coating compositions as shown in Table 1 below were prepared from thesecomponents. The stabilizers, which are supplied as solid powders, arenot rapidly soluble at normal ambient temperature in the mineral spiritssolvent predominantly used. Therefore, where indicated in Table 1 thesestabilizers were dissolved separately in a minimal amount of hot acetoneand added to the mixture in the resulting solution; the amount ofacetone required was never more than 1% of the amount of primary solventused and is not believed to have had any significant effect on theresults obtained. However, it was later learned that the stabilizerscould be dissolved without using any auxiliary solvent by raising thetemperature of the primary solvents, and this method was used in lateroperations.

The tacky and/or rubbery polymeric materials used were cut into smallpieces to facilitate dissolution and, in all the examples shown in Table1 dissolved adequately after stirring for no more than a few hours attemperatures up to 90° C. In some other tests not shown, attempteddissolution was not practical and the corresponding compositions werenot tested further.

The liquid compositions were applied to the substrates tested bybrushing, immersion, or spraying until a substantially uniform coatingover the desired area was obtained. The liquid coated substrate sampleswere then exposed to a temperature of 163° C. (unless otherwise notedbelow) in an air circulating oven and periodically observed until alldetectable tack had disappeared, or other indications of unsuitabilty,such as the apparent loss of most or all of the coating, had occurred.In some but not all instances, the liquid coated substrates were firstexposed for a time from a few minutes to about two hours to

TABLE 1 COATING COMPOSITIONS TESTED Additional Comp. Tacky Solid PrimaryStab. Stab. Solvent # # Parts of # Parts of # Parts of # Parts of  1 130 — None — None 1 70  2 1 30 2 0.3 — None 1 70  3 1 30 3 0.3 — None  1*70  4 1 30 1 0.3 — None  1* 70  5 1 28.4 1 0.57 — None  1* 71.6*  6 128.4 1 0.28 4 0.14  1* 71.6*  7 1 28.4 1 0.28 5 0.14  1* 71.6*  8 1 28.41 0.28 6 0.14  1* 71.6*  9 1 28.4 1 0.28 4 0.14  1* 71.6* 6 0.14 10 128.4 1 0.28 5 0.14  1* 71.6* 6 0.14 11 1 31.9 1 0.32 4 0.16  1* 68.1* 121 2.55 1 0.025 4 0.013  1* 5.45* 13 1 2.55 1 0.130 4 0.065  1* 5.45* 141 16.2 1 0.2 4 0.2 2 32.5 15 1 11.9 1 0.7 4 0.7 2 33.8 16 1 17.1 1 0.2 40.2 2 32.4 17 1 16.7 1 0.2 4 0.2 1 30.4 18 1 140 1 4 4 2 1 327 19 1 50 10.0625 4 0.0625 1 47.5 20 1 25 1 0.33 4 0.33 1 23.8 21 2 40 1 0.48 40.48 1 60 22 1 24 1 0.30 4 0.30 1 117 3 6 23 4 10 1 0.1 4 0.1 1 130Footnote for Table 1 *Relatively small amounts, compared to the solventshown, of acetone were used to predissolve the stabilizers and formedpart of the total solvent in the formulation as coated for formulationson lines in which this footnote symbol appears. Abbreviations for Table1 Comp. = Composition; # = Number; Stab. = Stabilizer(s)

a temperature of 110° C. in order to drive out most of the solventbefore beginning the high temperature aging tests. Results of the agingtests are shown in Table 2 below.

TABLE 2 AGING TEST CONDITIONS AND RESULTS Aging Sub- Ct. Comp. Test #strate # # Stability Indicator(s) 1A 1  1 1.2% of ct. wt. rtd. and dkd.after 64 hrs; dk. brown af. 14 days 1A′ 1  1 21% of ct. wt. rtd. af. 21hrs, <2% af. 50 hrs¹ 1S 2  1 Dkd. after 64 hours¹ 2A 1  2 1.4% of ct.wt. rtd. and dkd. after 64 hrs; dk. brown af. 14 days 2A′ 1  2 24% ofct. wt. rtd. af. 21 hrs, <2% af. 50 hrs¹ 2S 2  2 Dkd. after 64 hours¹ 3A1  3 36% of ct. wt. rtd. and 51 dkd. after 64 hours¹ 3A′ 1  3 37% of ct.wt. rtd. after 21 hrs, 33% af. 50 hrs.¹ 3S 2  3 Dkd. after 64 hours 4A 1 4 33 % of ct. wt. rtd. and udkd. after 64 hrs; same % rtd., v.s. yeld.af. 14 days; 4A′ 1  4 34% of ct. wt. rtd. and udkd. after 21 hrs. 4S 2 4 Dkd. after 64 hours; dk. brown af. 14 days 5A 1  5 Udkd. af. 24 hrs²;sl. yeld. af. 48 hrs; sl. m. yel. af. 5 days. 5S 2  5 Tack rtd. af. 24hrs²; 51 less tack af. 48 hrs; no tack af. 5 days. 6A 1  6 Udkd. af. 24hrs²; still udkd. af. 5 days 6S 2  6 Tack rtd. af. 24 hrs²; uchgd. af.48 hrs; no tack af. 5 days. 7A 1  7 Udkd. af. 24 hrs²; still udkd. af. 5days 7S 2  7 Tack rtd. af. 24 hrs²; uchgd. af. 48 hrs; no tack af. 5days. 8A 1  8 Udkd. af. 24 hrs²; sl. dkd. af. 5 days 8S 2  8 Tack rtd.af. 24 hrs²; uchgd. af. 48 hrs; no tack af. 5 days. 9A 1  9 Udkd. af. 24hrs²; still udkd. af. 5 days 9S 2  9 Tack rtd. af. 24 hrs²; uchgd. af.48 hrs; no tack af. 5 days. 10A 1 10 Udkd. af. 24 hrs²; still udkd. af.5 days 10S 2 10 Tack rtd. af. 24 hrs²; uchgd. af. 48 hrs; no tack af. 5days. 11A 4 11 Still tack after 7 days² 11S 2 11 No tack after 7 days²11C 5 11 Some tack lost af. 48 hrs; all tack lost af. 6 days 11T 6 11All tack rtd. af. 48 hrs; all tack lost af. 6 days 11G 7 11 All tackrtd. af. 48 hrs; all tack lost af. 6 days 11H 8 11 All tack rtd. af. 48hrs; all tack lost af. 6 days 12SS 9 12 All tack lost and si. yeld.after 7 days. 12SG 10  12 Dkd. but still rtd. original tack after 7 days13 2 13 No tack after 7 days. 14AS 3 14 Sl. dkd. but still tacky af. 14days; no tack af. 15 days 14S 2 14 Sl. dkd. but still tacky af. 14 days;no tack af. 15 days 15A 3 15 Coating in place af. 1 day except on upperpart of substrate 15S 2 15 No coating after 1 day. 16A 3 16 Rtd. tackfor 14 days; no tack after 15 days 16S 2. 16 Rtd. tack for 8 days; notack after 9 days 17A 3 17 Rd. tack for 19 days; no tack after 20 days17S 2 17 No tack after 5 days 18A 4 18 Rtd. full tack for 15 days³, sometack for 18 days; no tack after 19 days 18PCS 11  18 Rtd. tack after 7days³; no tack after 10 days 18S 2 18 Rtd. tack after 4 days³; no tackafter 7 days 19A 3 19 Sl. tack rtd. after 1 day; no tack after 2 days19S 2 19 No coating rtd. after 1 day 20A 3 20 Not dkd. and rtd. tackafter 6 days;.rtd. most tack after 8 days, with sl. coating loss 20S 220 Rtd. coating and some tack after 1 day; no tack after 2 days 21 3 21Retained tack after 14 days 22 3 22 Retained tack after 19 days 23 3 23Retained tack after 84 days; test then discontinued Footnotes for Table2 ¹Very little if any further change observed on further aging for 10days. These tests, because they were performed in pans, were withconsiderably thicker films than those tested on panels, which areconsidered more practical. Also, tack was not measured in any of thesetests. ²In these tests, the wet coated substrates were heated for onehour at 110° C. before beginning aging at higher temperature. ³Aging at176° C. General Note for Table 2 The symbol ′ after an aging test numbermeans that the aging was at 149° C. Additional Abbreviations for Table 2Ct. Comp. = Coating Composition; ct. wt. = coating weight; rtd. =retained; dkd. = darkened; hrs = hours; dk. = dark; af. = after; sl. =slight(ly); udkd. = undarkened; yeld. = yellowed; uchgd. = unchanged.

The invention claimed is:
 1. A liquid coating composition whichcomprises each of the following components (A)-(D): (A) an amount of acomponent of polymeric material that (i) is solid and (ii) has tacksufficient to be sensed by a brief touch by a normal human finger, boththroughout a temperature range from 25 to 160° C.; (B) an amount of acomponent of first stabilizing molecules and moieties thereof, exclusiveof molecules and moieties thereof that constitute component (A), each ofthe first stabilizing component molecules or moieties thereof containing(i) at least one benzene ring that is substituted with at least onehydroxyl moiety and at least two alkyl moieties and (ii) at least onecarbon atom bonded by single bonds to four other carbon atoms,alternatively called a “tertiary” carbon atom; (C) an amount of acomponent of second stabilizing molecules or moieties thereof, exclusiveof molecules or moieties thereof that constitute component (A) or (B),each of the second stabilizing component molecules or moieties thereofcontaining (i) at least one divalent sulfur atom that is bonded to twodistinct carbon atoms and (ii) at least two carboxyl or carboxylatemoieties; and (D) an amount of a component of solvent, exclusive ofmaterials that constitute part of any of the preceding components, thesolvent having a freezing point below 20° C. and a boiling range at apressure of 1 bar that begins at a temperature that is at least about70° C. and ends at a temperature that is not more than 230° C. and beingpresent in sufficient amount to dissolve together into a single solutionall of components (A), (B), and (C) to form a solution that is liquid at25° C., said liquid coating composition having the property that, when avolume of the composition is formed into a layer not more than 0.5millimeter in thickness and heated to at least one temperature notgreater than 160° C., in a space containing gas having a pressure nohigher than that of the ambient natural atmosphere, at least components(A), (B), and (C) of the composition will be converted within a time of60 minutes into a coherent tacky solid, and at least a preponderant partof component (D) will be volatilized.
 2. A liquid coating compositionaccording to claim 1, wherein: the amount of component (C) has a ratioto the amount of component (B) that is from about 0.10:1.0 to about2.0:1.0; the amount of component (B) has a ratio to the amount ofcomponent (A) that is from about 0.0010:1.0 to about 0.08:1.0; andcomponent (D) has a boiling range between about 100 and about 220° C. ata pressure of 1 bar.
 3. A liquid coating composition according to claim2, wherein: the amount of component (C) has a ratio to the amount ofcomponent (B) that is from about 0.90:1.0 to about 1.10:1.0; the amountof component (B) has a ratio to the amount of component (A) that is fromabout 0.0090:1.0 to about 0.0013:1.0; component (D) has a boiling rangebetween about 150 and about 180° C.; component (A) is selected from thegroup consisting of aliphatic hydrocarbon polymer molecules in whichcarbon atoms and carbon-carbon double bonds are present in respectivenumbers such that the number of carbon-carbon double bonds is notgreater than about 0.3 times the number of carbon atoms; component (A)has a Viscosity Average molecular weight that is not less than about1.0×10⁴ and is not greater than about 1.1×10⁶; component (B) is selectedfrom the group consisting of molecules in which all benzene ringspresent are substituted with at least one hydroxyl moiety and at leasttwo alkyl moieties, each of said alkyl moieties being bonded to saidbenzene ring via a carbon atom that is also bonded by single bonds to atleast two other carbon atoms within the alkyl moiety, one of said alkylmoieties being a substituent on each of both carbon atoms in the benzenering that are adjacent to each carbon atom in the benzene ring bearing ahydroxyl moiety substituent, and each of said alkyl moieties having from2 to 8 carbon atoms; each molecule or moiety thereof that constitutespart of component (B) also contains at least one carboxylate estermoiety through which at least one benzene ring of the molecule or moietythereof, said benzene ring having a hydroxyl substituent and at leasttwo alkyl substituents, is bonded to a tertiary carbon atom in saidmolecule or moiety thereof, said carboxylate ester moieties and saidbenzene rings being present in component (B) in respective numbers suchthat the number of said carboxylate ester moieties is not less than thenumber of said benzene rings; component (C) is selected from the groupconsisting of molecules containing a number of carboxyl and carboxylatemoieties, each of which is bonded via at least one of a total number ofdivalent alkylene moieties present in component (C) to one of a totalnumber of divalent sulfur atoms present in component (C), each of saiddivalent alkylene moieties being also bonded to a carboxylate ester ofan alcohol having from 6 to 22 carbon atoms per molecule, the totalnumber of said divalent alkylene moieties present in component (C) beingat least as great as the total number of divalent sulfur atoms presentin component (C).
 4. A liquid coating composition according to claim 3,wherein: component (A) is selected from the group consisting ofhomopolymers of isobutylene and copolymers of isobutylene and1,3-butadiene in which carbon atoms and carbon-carbon double bonds arepresent in respective numbers such that the number of carbon-carbondouble bonds is not greater than about 0.003 times the number of carbonatoms; component (A) has a Viscosity Average molecular weight that isnot less than about 5.0×10⁴ and is not greater than about 1.1×10⁶;component (B) is tetrakis {methylene3-(3′,5′-ditertiarybutyl-4-hydroxybenzene propionate} methane; component(C) is lauryl stearyl thiodipropionate; component (D) is selected frompetroleum mineral spirits and has a boiling range from 150 to 180° C.;and the solution of components (A), (B), and (C) in component (D) is notdispersed in any other liquid.
 5. A process for forming a surfacingmaterial suitable for the interior of baking ovens, said processcomprising steps of: (I) providing (i) a metallic substrate having atleast one surface constituted of not less than 90% of aluminum and (ii)a liquid composition according to claim 4; (II) forming at least part ofthe liquid composition provided in step (I) into a liquid coating with athickness that is from about 300 to about 500 μm over at least part ofthe surface constituted of not less than 90% of aluminum on thesubstrate also provided in step (I); and (III) heating, at a temperaturethat is not more than 170° C. and not less than a value obtained bysubtracting 10° C. from the upper limit of the boiling range, at apressure of 1 bar, of component (D) of the liquid composition providedin step (I), the liquid coating formed in step (II), while said coatingis in place over the substrate surface as formed in step (II) and theliquid coating is in contact with the normal ambient atmosphere toconvert the liquid coating to a solid, adherent, and tacky coating overthose portions of the substrate surface that were provided with a liquidcoating in step (II).
 6. A baking oven comprising interior surfacingmaterial made by a process according to claim
 5. 7. A process accordingto claim 5, wherein the metallic substrate provided in step (I) is atleast part of an interior surface within a heatable zone of a bakingoven.
 8. A baking oven modified by a process according to claim
 7. 9. Aprocess for cleaning a baking oven according to claim 8 that bearsaccumulated deposits of foreign material on at least part of itsinterior surface that is constituted of a coating formed according tosaid claim, said process comprising a step of heating said coating andthe accumulated deposits thereon in ambient natural atmosphere to atemperature at which the metallic substrate on which said coating isformed remains solid but said coating decomposes.
 10. A process forforming a surfacing material suitable for the interior of baking ovens,said process comprising steps of: (I) providing (i) a metallic substratehaving at least one surface constituted of not less than 60% of aluminumand (ii) a liquid composition according to claim 3; (II) forming atleast part of the liquid composition provided in step (I) into a liquidcoating with a thickness that is from about 30 to about 1000 μm over atleast part of the surface constituted of not less than 60% of aluminumon the substrate also provided in step (I); and (III) heating, at atemperature that is not more than 200° C., the liquid coating formed instep (II), while said coating is in place over the substrate surface asformed in step (II) and the liquid coating is in contact with the normalambient atmosphere, to convert the liquid coating to a solid, adherent,and tacky coating over those portions of the substrate surface that wereprovided with a liquid coating in step (II).
 11. A baking ovencomprising interior surfacing material made by a process according toclaim
 10. 12. A process according to claim 10, wherein the metallicsubstrate provided in step (I) is at least part of an interior surfacewithin a heatable zone of a baking oven.
 13. A baking oven modified by aprocess according to claim
 12. 14. A process for cleaning a baking ovenaccording to claim 13 that bears accumulated deposits of foreignmaterial on at least part of its interior surface that is constituted ofa coating formed according to said claim, said process comprising a stepof heating said coating and the accumulated deposits thereon in ambientnatural atmosphere to a temperature at which the metallic substrate onwhich said coating is formed remains solid but said coating decomposes.15. A process for forming a surfacing material suitable for the interiorof baking ovens, said process comprising steps of: (I) providing (i) ametallic substrate having at least one surface constituted of not lessthan 60% of aluminum and (ii) a liquid composition according to claim 2;(II) forming at least part of the liquid composition provided in step(I) into a liquid coating with a thickness that is from about 30 toabout 1000 μm over at least part of the surface constituted of not lessthan 60% of aluminum on the substrate also provided in step (I); and(III) heating, at a temperature that is not more than 200° C., theliquid coating formed in step (II), while said coating is in place overthe substrate surface as formed in step (II) and the liquid coating isin contact with the normal ambient atmosphere, to convert the liquidcoating to a solid, adherent, and tacky coating over those portions ofthe substrate surface that were provided with a liquid coating in step(II).
 16. A baking oven comprising interior surfacing material made by aprocess according to claim
 15. 17. A process according to claim 15,wherein the metallic substrate provided in step (I) is at least part ofan interior surface within a heatable zone of a baking oven.
 18. Abaking oven modified by a process according to claim
 17. 19. A processfor cleaning a baking oven according to claim 18 that bears accumulateddeposits of foreign material on at least part of its interior surfacethat is constituted of a coating formed according to said claim, saidprocess comprising a step of heating said coating and the accumulateddeposits thereon in ambient natural atmosphere to a temperature at whichthe metallic substrate on which said coating is formed remains solid butsaid coating decomposes.
 20. A process for forming a surfacing materialsuitable for the interior of baking ovens, said process comprising stepsof: (I) providing (i) a metallic substrate having at least one surfaceconstituted of not less than 45% of aluminum and (ii) a liquidcomposition according to claim 1; (II) forming at least part of theliquid composition provided in step (I) into a liquid coating over atleast part of the surface constituted of not less than 45% of aluminumon the substrate also provided in step (I); and (III) heating the liquidcoating formed in step (II), while said coating is in place over thesubstrate surface as formed in step (II), to convert the liquid coatingto a solid, adherent, and tacky coating over those portions of thesubstrate surface that were provided with a liquid coating in step (II).